The present invention relates to a fluid-operated wrench for tightening or loosening threaded connectors.
Fluid operated wrenches of the above mentioned general type are known in the art. Some of such wrenches are disclosed in my U.S. Pat. Nos. 4,409,865 and 4,368,658, and in my patent application Ser. No. 768,038 pending. In the known fluid-operated wrenches a driving element of drive means is connected with a driving arm in a connecting or leverage axis and pivots the driving arm about its pivot axis. During the pivoting of the driving arm about its pivot axis, the driving arm displaces and turns a respective one of two driving pawls turnable about their axes and turning a ratchet wheel of the wrench. The driving arm is constructed and arranged so that during the forward and the rearward strokes of the driving element of the drive means, the respective driving pawl turns the ratchet wheel in the same direction. The pivot axis of the driving arm is located between the turning axes of the driving pawls and is formed by a pin which extends through an opening in the driving arm. In order to achieve a high multiplying effect, the distances between the turning axis of one pawl and the pivot axis of the driving arm and the turning axis of the other pawl and the pivot axis of the driving arm should be kept as small as possible in comparison with the distance between the connecting or leverage axis and the pivot axis of the driving arm. In the known constructions the distances between the turning axes of the driving pawls and the pivot axis of the driving arm could be reduced only to a certain degree, simply because the guide which insures pivoting of the driving arm about its pivot axis was formed by the above mentioned pin-opening located between the turning axes of the driving pawls, with the respective consumption of the material between the turning axes. Therefore for achieving the required force multiplying effect, the distance between the connecting or leverage point and the pivot point of the driving arm was relatively long, the size of the wrench was big and therefore it was relatively heavy.